Thermal blanket



I. JEPSON THERMAL BLANKET July 3, 1956 2 Sheets-Sheet 1 Filed April 25, 1954 INVENTOR. W72

H H HR M\ nnuuuvvunu k THERMAL BLANKET Ivar Jepson, Oak Park, Ill., assignor to Sunbeam Corporation, Chicago, 111., a corporation of Illinois Application April 23, 1954, Serial No. 425,192

31 Claims. (Cl. 21--3) The present invention relates to thermal blankets, and, more particularly, to blankets having heat transfer means included therein whereby the temperature of the same may be controlled in a desired manner.

So-called electric blankets have been extensively sold in recent years to take the place of blankets generally used in homes, hospitals and the like. The electric blanket has proven to be desirable, particularly in cold climates, since it supplies the necessary heat without the weight that otherwise is required by employing enough ordinary blankets to furnish the equivalent warmth. Moreover, such electric blankets generally have suitable control means whereby one using the same may control the heat supplied in any desired manner. Electric blankets employ a grid of electric conductors embodied in some way in the fabric of the blanket. Obviously, these conductors are insulated with suitable insulating material.

The first electric blankets to come on the market employed a step-down transformer, so that the person sleeping under the blanket would not be subjected to line voltage in the event that defective insulation or the like permitted him to come in contact with the electric grid contained in the blanket.

A more common problem in connection with electric blankets is that during use the blanket becomes bunched or folded, or after use is rolled up at the bottom of the bed while still energized. Under such conditions the heat loss from the folded or rolled section of the grid or heating conductor in the blanket is greatly reduced. This tends to cause localized heating, with the attendant possibility of tire. In order to preclude the possibility of such local overheating, there have been incorporated at selected positions in the electric blankets numerous thermostats, so that overheating in any one of these selected areas causes the associated thermostat to operate to open at least the portion of the heating circuit causing trouble and thereby deenergizing a section of the heating conductor for the blanket. It will be obvious that the number of such localized thermostats must be relatively great in order to alford the desired protection, since the blanket might be rolled or folded at many different points.

Even though electric blankets might be entirely safe in every respect, there is the psychological factor that is involved in that persons are sometimes afraid to use them because of the nature of the device, namely, sleeping under an electrical device which has the remote possibility of shocking the person using the same, and the greater possibility, even though also remote, of being a fire hazard. The fire hazard problem becomes greater when it is considered that bedding, in general, is very inflammable material. Electric blankets can only be used for heating purposes and do not lend themselves to use as a cooling blanket.

Although electric blankets have been made relatively light in weight as compared with the blankets which they displaced where no heating means were employed, nevertheless a substantial weight is still involved in order to hired States Patent accommodate the necessary insulated copper conductors and the numerous local thermostats which must be employed for protective purposes.

It will be appreciated that electric blankets must be cleaned periodically, whether by washing or by dry cleaning. Many manufacturers have constructed electric blankets in a manner to permit washing thereof. Obviously, this introduces problems, since the local thermostats used throughout the blanket must be waterproofed and protected. Likewise, the electrical installation must be such as to preclude the cleaning material such as water from coming into contact with the electrical conductors.

it would be desirable to provide a thermal blanket which would have all of the advantages of an electric blanket without the problems of electrical shock, fire hazard and the like, and which may be made even lighter in weight than electric blankets as presently sold. It would also be desirable to provide a thermal blanket which can be used not only for heating purposes as can an electric blanket, but which is adaptable for performing a cooling as well as a heating function. Likewise, it would be de sirable to provide a thermal blanket which may be washed or cleaned as often as desired without any of the problems which existed in connection with electric blankets.

Accordingly, it is an object of the present invention to provide a new and improved thermal blanket.

it is another object of the present invention to provide a thermal blanket which may be lighter in Weight than blankets heretofore employed with built in means for heating the same, and which may be utilized for heating or cooling functions.

It is a further object of the present invention to provide a thermal blanket which includes simple heat transfer means capable of providing the desired heating or cooling, which is completely safe in every respect, and which lends itself to ready cleaning.

It is another object of the present invention to provide a thermal blanket which may be used with complete freedom without worry of electric shock or fire.

Still another object of the present invention resides in an improved control arrangement for a thermal blanket whereby any desired temperature may be supplied by the blanket.

Still a further object of the present invention resides in the provision of a thermal blanket wherein a fluid is circulated therethrough and improved means for circulating the fluid including a substantially noise and vibration-free motor driven pump unit is provided.

It is another object of the present invention to pro vide a circulating unit for a thermal blanket comprising a sealed motor and pump unit in which the heat transfer fluid serves as a cooling medium for the motor windtags.

it is another object of the present invention to provide in connection with a thermal blanket a motor and pumping unit for circulating a fluid through said blanket, which motor and pumping unit is insulated from the surrounding air by sound and heat insulating barriers, and means are provided for cooling the motor by means of the fluid circulated through the thermal blanket by the pump.

It is another object of the present invention to provide in connection with a thermal blanket an improved control means responsive directly to the temperature of the return fluid for insuring accurately controlled ternperature at all times.

It is another object of the present invention to provide in a thermal blanket an improved means or circulating the fluid through the blanket, which means is small and compact, sound and vibrationproof, and wherein the thermal blanket and the means for circulating the fluid therethrough may be disconnected in a simple manner with the fluid completely removed from the blanket and contained in the circulating unit.

Further objects and advantages of the present invention will become apparent as the following description proceeds, and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the present invention, reference may be had to the accompanying drawings in which:

Fig. l is a perspective view illustrating an application of the thermal blanket of the present invention;

Fig. 2 is a plan view of the thermal blanket of the present invention with certain portions of the blanket fabric turned back better to illustrate the thermal means associated therewith, and with the fluid connections thereof disclosed in the position normally assumed when the blanket is disconnected from the fluid circulating unit;

Fig. 3 is an enlarged view of a portion of the thermal means in the blanket of Fig. 2;

Fig. 4 is a seectional view taken on line 44 of Fig. 3;

Fig. 5 is a schematic diagram illustrating the details of the fluid circulating unit and the electrical circuit included in the thermal blanket and circulating means therefor of the present invention;

Fig. 6 is a sectional view taken through the fluid circulating unit of Fig. 1;

Fig. 7 is an enlarged sectional view taken on line 77 of Fig. 6; and

Fig. 8 is a curve diagram to aid in understanding the operation of the thermal blanket of the preesnt invention.

Briefly, the present invention is concerned with a thermal blanket employing no electrical conductors therein, but, instead, a plurality of small tubes, all connected in parallel to headers at the foot of the blanket, through which a suitable heated or cooled fluid may be circulated, as the case may be. The arrangement of the tubes is such that the blanket has a substantially uniform temperature throughout. Suitable control means are provided automatically to control the temperature of the blanket in dependence upon the ambient temperature of the room in which the blanket is employed. The control means is preferably embodied in a control unit which also circulates the fluid through the blanket, which control unit is simple and compact and which embodies heating or cooling means for the fluid to be circulated. Specifically, the control unit includes, in addition to the heating or cooling means, means for circulating the fluid through the blanket and a thermostat for controlling the temperature of the fluid being circulated, the operation of which thermostat may be manually controlled by the user of the blanket to give. any desired blanket temperature within determined temperature ranges.

Referring now to the drawings, there is illustrated in Fig. l the thermal blanket l0 embodied in the present invention, which blanket is shown as being applied to a suitable bed 11. The fluid passageways defined in the blanket 10 of Fig. l are only very schematically indicated, but are clearly shown in Fig. 2 of the drawings. In any event, in accordance with the present invention, there is provided a suitable control and fluid circulating unit, generally designated at 12, which is illustrated as being disposed at the foot of the bed 11, preferably to provide for short fluid connections between the unit 12 and the blanket ll). Obviously, this unit 12 may be disposed in any suitable manner and may be set on the floor as indicated or may be supported on suitable rack means or the like associated with the bed 11. The unit 12 includes a suitable control knob 13 for adjusting the desired temperature selected by the user. If desired, this control knob 13 may be incorporated in a separate unit which could be disposed on a night table adjacent the head of the bed 11, but, preferably, and as illustrated in the drawings, the control means is all incorporated in the unit 12. A suitable power cord 14 is. illustrated as extending from the control unit 12 to a conventional outlet plug 15 connected to a conventional electric outlet 16 disposed in any suitable manner in the room within which the bed 11 is disposed.

In accordance with the present invention, the thermal blanket 10, best shown in Fig. 2 of the drawings may be formed of any desirable fabric. The particular fabric from which the blanket of the present invention is constructed is immaterial as far as the present invention is concerned. It should comprise a fabric which has a pleasing appearance and may have any desired color to harmonize with the color scheme which may be involved where the blanket is being used. The blanket 10 may comprise one fabric member having passageways woven therein or as illustrated may comprise two layers of fabric designated as 19 and 20 which are superimposed and which may have the conventional binding 21 around the edge thereof so as to give the appearance of any ordinary blanket. The two superimposed fabric layers 19 and 20 are fastened together by a plurality of parallel rows of stitching designated by the reference numeral 23. This stitching runs from the foot end of the blanket to the head end, and terminates just short of the binding at each end, as is clearly indicated in Fig. 2 of the drawings, to define an open passageway of fairly narrow extent across both the head end and the foot end of the blanket just inside the binding 21. The passageway across the head end of the blanket is designated by the reference numeral 24, while the passageway across the foot end of the blanket is designated by the reference numeral 25'. The parallel passageways between the stitchings 23 leading from the passageway 24 to the passageway 25 are defined by the reference numeral 27. It will be appreciated that the same general construction is involved when a single fabric member having passageways 27 woven directly therein is employed.

For the purpose of converting the blanket 3b to a thermal blanket, there are disposed within the passageway 25 a pair of parallel headers designated by the ref erence numerals 28 and 29. The header 2.8 may be designated as the blanket inlet header, while the header 29 may be designated as the blanket outlet header. These headers may be of identical configuration, and the header 25 is shown in greatly enlarged form in Figs. 3 and 4. Preferably the headers are formed of plastic tubing, and, for reasons which will become apparent as the following description proceeds, the plastic tubing preferably comprises tubing formed of polyvinyl chloride with certain plasticizers added, which is hereinafter referred to as polyvinyl chloride tubing. To provide the desired heat transfer and still provide a sufficiently light weight, the headers 23 and 2?. which may be identical in construction, have an internal diameter of between 0.09 and 0.2 of an inch, with a wall thickness of between 0.02 and 0.05 of an inch. In a preferred embodiment constructed in accordance with the present invention, the headers 23 and 29 were formed of polyvinyl chloride having an internal diameter of 0.095 of an inch and a wall thickness of 0.04 of an inch. It will be understood that the headers 28 and 2B are adapted to supply a suitable thermal fluid to the blanket 10.

in order uniformly to distribute the thermal fluid supplied by the header 28 throughout the area of the thermal blanket 14 there are provided a plurality of small tubes designated by the reference numeral 31. These tubes are indicated as disposed in the form of a U or hairpin, with the bight portion of the U at the head end of the blanket, and the ends of the arms or legs of the U connected to the headers 28 and 29, respectively. With this arrangement all of the loops 51 are connected in parallel with each other. In accordance with the present invention, each arm of the loops 31 is disposed in a separate passageway 27, thus assuring that the loops will remain in the desired position within the blanket 10. Preferably the loops 31 are defined by small tubing also formed from a suitable plastic such as polyvinyl chloride, and preferably are substantially smaller tubes than are those which comprise the headers 28 and 29. To insure the necessary heat exchange and at the same time to provide a blanket of very light weight, the tubes 31 preferably have an internal diameter of between 0.025 and 0.075 of an inch, and a wall thickness of between .016 and .030 of an inch. In a preferred embodiment constructed in accordance with the present invention, sixteen loops such as 31 were employed in a standard size blanket, thus providing thirtytwo passageways 27, with thirty-two arms of the loops 31 disposed one in each passageway. The tubes 31 in this blanket constructed in accordance with the present invention had an internal diameter of .042 of an inch and a wall thickness of .025 of an inch. It Will be understood that the number of loops employed and the size of the tubes 31 and the headers 28 and 29 may be varied somewhat, although the particular arrangements described have been found to be very satisfactory and provide a substantially lighter blanket when all the tubes are filled with the fluid to be circulated than conventional electric blankets employing the identical fabrics such as 19 and 20.

The connections between the headers 28 and 29 and the loops 31 may be made in the manner best shown in Figs. 3 and 4- f the drawings. The headers 28 and 29 will be provided with a plurality of spaced openings such as (Fig. 4 of the drawings) for completing the passageways between the headers and the loops 31. Suitable adapters 36, also formed of polyvinyl chloride or similar material, may be employed which have a yoke portion 36a for receiving therein a substantial portion of the contour of the header 28 or 29. The adapter 33 may be heat-sealed to the header. The adapter 36 is such as to receive therein the end of one arm or leg of the U- shaped tube 31, as clearly indicated in Figs. 3 and 4 of the drawings, which may also be heat-sealed thereto to complete the closed fluid passageways through the blanket.

Because of the number of joints required between the headers 28 and 29 and the tubes 31, it is desirable that the tubing employed should lend itself to heat sealing by the use of high frequency electric currents. It is for this reason that polyvinyl clnoride tubing has been suggested as the most desirable, since excellent seals can be made by the high frequency method When polyvinyl chloride tubing is employed. It will be understood that other plastics can be employed for the tubing, such, for example, as polyethylene tubing. Unfortunately, polyethylene tubing cannot be readily heat-sealed, and if it is desired to use polyethylene for the tubing then other methods for making the joints between the tubing and the headers will be required. It will be appreciated that the type of material chosen for the headers and tubing will also to some extent govern the heat exchange fluid to be circulated therein, for the fluid must be one that will not attack the tubing and must be compatible therewith.

In applying the thermal means comprising the headers 28 and 29 and the U-shaped tubes 31 to the blanket 10, the superimposed fabric portions 19 and 20 are first stitched with the stitchings 23 to define the passageways 27 in the event that the blanket comprises two fabric portions. Actually, the tubing could be stitched or otherwise secured to a single fabric sheet, although it is preferably inserted within passageways. One of the headers such as 28 or 29 is then connected to the corresponding arms of all of the U-shaped members 31. With the U-shaped tubes 31 straightened out, the arms not connected to the header are then inserted in the passageways 27 from the foot end of the blanket until the particular header connected to the tubes 31 is moved into the passageway 25. It will be understood that the tubes 31 are inserted in alternate passageways 27. The ends of the tubes 31 not connected to the header are bent back upon themselves and returned through those passageways within which no arms of the tubes 31 are disposed, whereby the two arms of each U- shaped tube are in adjacent passageways 27. The other header may then be moved into the passageway 25 and connected to the free ends of the tubes 31. The desired heat-sealing operation is then performed, so that the headers and tubes are connected together in sealed relationship. Thereafter the binding 21 may be applied to the blanket.

in order to connect the headers 28 and 29 to suitable fluid circulating means, each of the headers 28 and 29 is provided approximately in the middle thereof with a suitable coupling member. As illustrated, the header 23 is provided with a coupling member 38, while the header 29 is provided with a coupling member 39. These coupling members may also be formed of suitable plastic and sealed to the headers in any desired manner. Effectively, the coupling members 38 and 39 are T couplings and are respectively connected with blanket inlet tube 40 and blanket outlet tube 41. To insure a minimum temperature drop into the tubes 4r: and 41, they are preferably very short. Also in accordance with the present invention, these tubes are provided at their ends not connected to the headers 28 and 29 with suitable coupling members 42 and d3, respectively, best shown in Pig. 5 of the drawings. The coupling member 43 is a male type coupling member, and the coupling member 42 is a female type coupling member, so that the two may be interconnected as shown in Fig. 2 of the drawings when the blanket is not in use, whereby any fluid contained therein may not leak out. Normally, when the blanket 10 is stored, no fluid will be contained therein, but this provides a necessary precaution. It is immaterial whether the male or female connection is associated with the tube 40 or 41, and, obviously, the tubes 40 and 41 in normal use are adapted to be connected to a suitable circulating unit which will have corresponding coupling units, so that when the blanket is connected or disconnected from the circulating unit it will always be connected correctly. Thus in the inlet header 28 is supplied with the proper fluid, and the outlet header 29 returns to the circulating unit the fluid which has passed through the passageways in the blanket 10.

Considering that the thermal blanket 10 is used for heating rather than cooling, and assuming that there is no heat loss in the headers 28 and 29 and that the temperature of the header 28 along the length thereof is uniform, with the inlet temperature up to 20 F. higher than the temperature of the fluid in the header 29, it will be apparent that the warmest fluid will enter the leg of the tube 31 connected to the header 28 and will gradually cool, so that a temperature midway between the temperatures of the fluid in the headers 28 and 29 exists in the fluid in the bight of each U-shaped tube 31. The temperature continues to drop at a fairly uniform rate between the bight of each U-shaped tube and the outlet header 29. Thus, although there is a substantial temperature differential between the inlet and outlet temperatures of each tube 31, the average temperature produced by a particular loop along the length thereof is uniform and equal to the temperature at the bight of each U-shaped tube. This can best be observed from the curve diagram of Fig. 8 of the drawings. In the graph or curve diagram of Pig. 8, temperatures are plotted as ordinates, and distances along the tube 31 are plotted as abscissae. The loop 31 is schematically indicated in Fig. 8 to aid in understanding the curve diagram. As illustrated, the dashed line curve A represents the temperature drop along the leg of the tube 31 connected to the inlet header 23, while the curve B represents the temperature along the the leg of the tube 31 connected with the outlet header 29. These curves A and B are designated as straight lines, although actually they may deviate somewhat from straight lines. For the sake of illustration, however, they may be indicated as straight lines. it will be apparent that the curve C indicates a constant temperature midway between the curves A and B and is the average temperature along the loop 31 from the head to the foot of the blanket. Thus, it will be apparent that a substantially uniform average temperature will occur throughout the entire area of the blanket. Since the couplings 3S and 35B are disposed at the midpoint of the headers 28 and 2), respectively, a minimum temperature drop along the headers is assured, and further assuring uniform temperatures from one end of the blanket to the other. Although a heating blanket has been speci cally considered, it is apparent that a cooling blanket might equally well be employed, the same principles with respect to uniform temperature throughout the blanket area would also obtain.

in accordance with the present invention it is desired to provide the thermal blanket 10 when operating as a heating blanket with the ability to dissipate 280 Watts of energy when operating at its maximum capacity. This is comparable with electric blankets now on the market which have a capacity of 180 watts or thereabouts. Actually, it would be more appropriate to express the energy in the present blanket in B. t. u.s, but for comparison with electric blankets the corresponding energy terms will be employed. it will be understood that to dissipate this amount of energy, it is necessary to determine the rate of flow of fluid through the passageways and also the temperature differential between the fluid in the inlet and outlet headers. Preferably and in accordance with the present invention, a constant flow of fluid is employed, which, as will become apparent from the following description, is maintained whenever the blanket is in use. In a particular embodiment constructed in accordance with the present invention, a fluid flow of the order of ten ounces per minute was chosen. Obviously, a higher rate of flow may be employed, but the ten ounce per minute rate of flow has been found satisfactory, since a lower pump capacity is required. Two hundred watts of energy will be dissipated in a blanket of the type described and disclosed in Pig. 2 of the drawings if ten ounchcs per minute of water is caused toflow through the blanket, and a temperature differential of approximately 18 F. between the inlet and outlet fluid exists. The rate of flow is that through the tubes 4d and 41, and the inlet and outlet temperatures are those in the passageways 44) and 41.

Before considering the details of construction of the circulating and control unit 12, it should be noted that the plastic tubing employed in the thermal blanket of the present invention including the headers 23 and 29, the U- shaped tubing 31 and the tubes 40 and 41 should be formed of a n aterial which has good extrusion properties. It shoulc, moreover, be capable of being subjected to temperatures in the range of 150 F. to 0 without any detrimental effect, and it must have good heatsealing properties so that the joints in the tubing can be made by high frequency heat-sealing process. Polyvinyl chloride tubing has all of the above properties. Since the present invention should also be capable of use in connection with cooling blanket, the wide temperature range is required. Furthermore, one should be capable of transporting the thermal blanket with the fluid contained therein in col temperatures without damaging the tubing and the like.

Also, before considering the details of construction of the control and circulating unit 12, consideration will be given to a suitable heat transfer fluid for circulation within the thermal blanket. This fluid must be pumped through tubes of very small diameter, as described above, for the purpose of transferring 200 watts of heat energy from the control unit 12 to the tube system in the thermal blanket 16. Preferably the fluid will be heated to a maximum temperature of 130 F. before leaving the control unit 12, and should not drop more than 18 when passing through the tubing of the thermal blanket. Such 8 fluid should have a high heat capacity and a very low viscosity, respectively, to reduce the volume of fluid to be circulated to a minimum and to avoid high pumping pressures. It should preferably also have good lubricating properties so that it may be utilized to lubricate the bearings of the circulating means. The fluid must, furthermore, have no corrosive or detrimental effect whatsoever with respect to the circulating means, nor should it have any detrimental effect on the plastic tubing employed. The fluid should preferably be water solublc so that any spilled fluid can be washed up with soap and water, and it should be nonstaining when coming in contact with wool or cotton materials. It should have a high heat capacity and good heat transferring properties so it may be used as a good heat transfer fluid and will also cool the motor and pump units employed. It should, furthermore, not freeze at temperatures as low as 0 F. One fluid that has been used satisfactorily is distilled water, which has a very low viscosity and meets substantially all of the qualifications except that it is not a good lubricator. Distilled water with a suitable antifreeze can be employed to meet the low temperature qualifications. Actually, a light hydrocarbon fluid has been found to be very satisfactory, having the low viscosity and also providing a good lubricant and a good heat transfer agent without being detrimental to the motor or windings thereof, which it should preferably cool.

The control until 12 of the present invention is best illustrated in Figs. 6 and 7 of the drawings, and also schematically illustrated in Fig. 5 of the drawings. it will be appreciated that this control unit must incorporate some form of pump for circulating fluid through the tubes defined in the blanket 10 described above. This pump might be one that utilizes the vapor pressure of the circulating fluid as the force to cause propulsion of the fluid through the tubes. It will be appreciated that since the circulating pump is operated in a bedroom close to a sleeping person, it is important that the operation of the pump and associated means be as quiet as possible. A pump utilizing the vapor pressure of the fluid to perform the pumping operation will obviously be very quiet. However, in accordance with the present invention there has been disclosed a mechanical pump unit which has been found to be very satisfactory and very quiet, so that no problem of having it operate in a bedroom with a sleeping person is involved, and, if anything, the noise and vibration produced by the same are less than that of the conventional electric clocks so commonly employed in bedrooms. As illustrated in Fig. 6 of the drawings, the control unit 12, including a motor and pump arrangement, is completely enclosed in a sound-absorbing outer container or housing 56, pref erably made from a suitable plastic. As illustrated, the housing comprises a main housing portion 5% and a cover portion 50/), both formed from a molded plastic and suitably united to provide a completely enclosed housing. A suitable opening 51 provided in the cover 5% accommodates the control knob 13.

For the purpose of circulating the thermal fluid through the blanket it there is provided within the housing 50 a sealed motor and pump casing 52 withi. which is disposed at suitable electric motor generally designated by the reference numeral 53, and a fluid pump generally designated at 54. The volume of the motor and pump casing 52. is very small, and in an embodiment constructed in accordance with the present invention no dimension of the casing 52 exceeded five inches. As illustrated in the drawings, the casing 52 is formed in two sections 52a and 5211, each of which is sort of a cup-shaped portion which are joined as indicated at to provide a sealed casing, and, hence, a completely sealed container for the motor 53 and the pump 54.

It will be appreciated that the motor 53 may drive any suitable circulating pump, and, as illustrated, the pump 54 comprises a vane type fluid pump comprising a pump housing 56 having defined therein a suitable pump chamber 57 within which is rotatably mounted a pump rotor 58 with which is rotatable a suitable vane 59 preferably formed of a suitable plastic such as Teflon. The pump rotor 58 is preferably a circular rotor having a groove cut therein to receive the pump blade or vane 59. The chamber '7 is preferably a symmetrical chamber with the upper half as viewed in Fig. 7 defining an Archimedes spiral of gradually increasing size beginning with the left-hand side as viewed in Fig. 7, while the lower half is an identical Archimedes spiral of decreasing size as viewed beginning with the right-hand side of Fig. 7. Thus, the dimension at any point across the chamber 57 through the center of the rotor 58 will be constant to accommodate the blade 59. Defined within the pump housing 56 is a suitable inlet passageway 60 and a pump outlet passageway 61. The inlet passageway 60 is defined at the lower portion of the pump as mounted within the pump casing 52, so as to be normally below the level of the fluid to be circulated by the pump 54, which fluid is designated by the reference numeral 62 in Figs. 5 and 6 of the drawings. In normal operation of the blanket the fluid may have the level indicated in Fig. 6 of the drawings. The motor casing 52, however, is suificiently large to contain all the fluid, so that the fluid contained in the blanket 10 may be transferred to the casing 52, as will become apparent as the following description proceeds.

The pump outlet passageway 61 is connected by suitable means including the coupling 63 and the tube 64, which leads outside the sealed casing 52 and also outside the sound and vibrationproof housing 50, as is clearly shown in Fig. 1 of the drawings. Preferably the tube 64 is relatively short where it extends outside the housing 50 and is provided with a suitable coupling member 65 to make connection with the coupling member 42 associated with the blanket inlet passageway 40. Since the blanket inlet passageway coupling 42 has been indicated as a female coupling, the coupling 65 is a male coupling, thereby insuring that the proper fluid connections are made when the blanket 10 is connected to the pump and control unit 12.

For the purpose of rotatably supporting the pump rotor 58 within the ump housing 56, a suitable bearing 67, which may be a bronze bearing or the like, is provided to accommodate a suitable shaft 69 extending from the one end of the pump rotor 58. The other end of the pump rotor 58 is preferably connected to means including a shaft '79 having an enlarged portion 70a which is suitably connected as by a press fit or the like with an extension 58a of the pump rotor 58. With this arrangement the pump rotor 58 and the extension 58a may be slotted to permit the ready insertion of the pump vane 59, after which the press lit between portions 58a and 70a may be completed, whereby the shaft 70 effectively comprises an integral extension of the pump rotor 58. The shaft 79, furthermore, supports the rotor 71 of the motor 53.

The motor 53, as is best shown in the schematic diaram of Fig. 5 of the drawings, is illustrated as the wellknown shaded pole motor having the magnetic structure '72 defining a suitable stator to provide a path for the flux produced by a winding 73, which flux passes through a suitable air gap and the rotor 71. A pair of brackets 74 and '75, suitably secured to the motor 53, support a suitable bearing '77 and the pump housing 56, respectively. Preferably also a suitable flange 7 8 closes the pump housing 56. The bearing 77 accommodates a portion of re duced diameter of the shaft 70 and also may include a suitable thrust bearing. Such a thrust bearing is indicated at St), and a suitable adjustable screw 81 threaded into one end of the bearing 77 controls the adjustment of the thrust bearing 80. The rotor 71 is the conventional squirrel cage rotor employed with shaded pole type motors, and, as illustrated in the drawings, is almost completely immersed in the fluid 62. It is, consequently,

16 important that the fluid 62 be one that is not detrimental to the motor 53. With this arrangement it will be apparent that it is not important to have elaborate sealing glands and the like for the pump 54, since any escape of fluid will be within the casing 52 and will do nothing except to lower slightly the efficiency of the pump 54. As illustrated and by virtue of the brackets 74 and 75, the motor 53 and the pump 54 are effectively a single unit and this unit is suitably supported within the casing 52. as by means of brackets 83 riveted or otherwise secured to the casing 52.

For the purpose of supporting the sealed casing 52 within the housing 50 in a manner so as not to transmit any vibrations and noise to the exterior of the housing 56, suitable resilient material such as sponge rubber or the like may be interposed between the casing 52 and the housing 50. Preferably, however, there is secured to the casing 52, and specifically to the upper portion of the casing 52, as viewed in Fig. 6 of the drawings, a support member 85. This support member 85 and also the casing 52 are then supported by suitable springs 86 from suitable support means 87 secured within the housing 56. With this arrangement the motor-pump unit 53-54 disposed within the sealed casing 52 is sus ended on tension springs, one located at each of the four corners of the casing, so that any vibrations or noise will not be transmitted to the exterior of the housing 50, and hence the unit 12 will be completely quiet and noise-free. To protect the spring support for the sealed casing 52 in the event that the housing 51 is handled roughly or turned upside down, the ends of the support 85 preferably engage suitable stops such as the shoulders 83 defined on the cover 50b. A relatively small space need be disposed between the support 85 and the shoulders 88 or any other suitable stops to permit the vibration-free support and at the same time to protect the device should it be turned upside down or handled roughly.

From the above description it is apparent that there is provided an arrangement for circulating a heat transfer fluid through suitable passageways defined in the blanket 10. Obviously some means must be provided to control the temperature of the fluid being circulated. If the blanket is to be used as a cooling blanket, suitable cooling means must be provided to cool the fluid to be circulated. Although the present invention is equally applicable to a cooling blanket as well as a heating blanket, the more general application is likely to be for heating purposes, and, as illustrated in the drawings, suitable means are provided to heat the fluid 62 circulated by the pump 54. Accordingly, there is rovided a heating element 99 disposed in heat exchange relationship with the fluid 62. This heating element 92 may be immersed within the fluid 62 or it may be disposed in heat exchange relationship with the sealed casing 52 which contains the fluid 62. in the drawings the heating element fit) is indicated as being disposed in heat exchange relationship with the casing 52. It is illustrated as a sheathed type heating element in which a coiled resistor 91 is disposed centrally of an outer sheath 92. The space between the resistor 91 and the sheath 92 is preferably filled with an electrical insulating material 93 which is a good conduotor of heat. Such sheathed heating elements are exten sively sold on the market today, and the construction thereof forms no part of the present invention except insofar as the heating element is disposed in a somewhat C-shaped configuration disposed in intimate heat exchange relationship with the bottom of the casing 52,, as viewed in Fig. 6 of the drawings. As illustrated there, the casing 52 is rovided with a suitable deformation 9 to receive the C-shaped portion of the sheathed heating element 9t) and insure mroe intimate heat exchange therewith. The sheathed heating element may be brazed or otherwise secured to the casing 52. The ends of the C-shaped sheathed heating element designated as 99a and 99b in Fig. 6 of the drawings extend up along one side of the casing, and suitable terminals 96 and 97 are provided for this heating element, which terminals are connected by conductors 98 and 99, respectively, with suitable control means and a source of power as described in detail hereinafter.

In view of the fact that the sealed motor and pump casing 52 is mounted within an insulating housing 59, a problem of dissipating the heat produced by the motor 55 is raised. Preferably and in accordance with the present invention, the fluid 62 is employed to cool the motor 53. If desired, the fluid 62 can be passed through suitable passageways in the rotor 71 of the motor 53. In such case, for example, the squirrel cage rotor bars may comprise brass or copper tubes through which the fluid may be circulated. Preferably, however, in the case of a thermal blanket used for heatnig, the return fluid from the blanket, which is at a reduced temperature, is caused to flow over the motor windings to cool the same. To this end return fluid from the blanket 1i passing through passageway 41 and coupling member 423 passes through a coupling member 10%) and pasageway 1&1 into housing and thence into a small boxlike metal container 1112 insulated from but secured to the exterior of casing 52 within housing 51), the purpose of which will become apparent as the following description proceeds. As illustrated, the small boxlike container 1&2 is connected by means of an insulating tube 103 with the interior of the sealed casing 52. The insulating tube 1G3 is dsiposed directly above the winding 73 so that the return circulating fluid, as schematically indicated in Fig. 5 of the drawings, flows over the winding '73 to cool the same. As also illustrated in Fig. 5 of the drawings, since the coupling 43 has been illustrated as a male type coupling, the coupling 19% is a female type coupling. With this arrangement it will be imposisble to make incorrect conections between the control unit 5i) and the blanket 11). Obviously, however, due to the symmetry of the headers 28 and 29, it is immaterial which is the supply header and which is the return header. However, by using the coupling arrangements disclosed, couplings 42 and 43 may be interconnected, and couplings 1'91) and 65 may be interconnected, so that when the blanket is disconnected from the control unit 12 no fluid can escape from either blanket 1% or unit 12.

in the conventional electric blanket employed heretofore, as was mentioned above, a number of thermostats we. provided which wcrc placed at different locations in the l; anket. in one blanket on the market today, about nine such thermostats are employed. These thermostats are set at a slightly higher temperature than the blanket should operate at, and are used only as safety means in the event of misoperation. Such thermostats cannot control the blanket temperature under normal operation. the purpose of controlling such electric blankets, there has been provided a thermostatic device remotely located from the blanket, which is used to select the de gree of warmth decided upon by the user. With such electric blankets there is no direct temperature sensing medium that connects the control device with the blanket itself except the air in the room. Due to drafts and uneven temperatures in the room, it is impossible for such remote temperature control device to sense accurately the temperature conditions in the electric blanket. There has been an attempt in electric blankets to make the rem ely located control device respond in some fashion ap hing the blanket condition by introducing an auxiliary ent the controlling thermostat. Even ction of the heat output of such auxilc-.t cannot accurately sense the temperature conn 111 the blanket. in the thermal blanket of the present invention, however, the fluid circulating through the ket is not only used to transfer heat to the blanket where the blanket is used for heating purposes, but it also provides a temperature sensing medium which can transfer information with respect to temperature conditions in the blanket directly to a suitable temperature responsive unit. In accordance with the present invention, the temperature of the return fluid from the blanket 1b is employed, and with the present invention it can be seen that the blanket itself constitutes a temperature sensing element, and it can transfer this information to the thermostat by means of the circulating fluid and do so immediately and with great accuracy. Thus, if the temperature of the blanket drops, the circulating fluid will cool to a greater extent and immediately call for more heat. in accordance with the present invention, therefore, there is provided a temperature responsive device illustrated as a bimetallic element 111), which has one end thereof in good heat conductive relationship with the boxlike container into which return fluid from the lanket 11b is supplied. Actually, the exit passageway comprising the tube 193 leading from the box 192 provides an outlet substantially smaller than the inlet to the box 192, so that in normal operation the latter is full of returning fluid and the bimetallic element 119, therefore, accurately responds to the temperature of the fluid returning from the blanket 10.

For the purpose of insulating the container 162 from the casing 52 for the motor and pump unit, the former is suitably supported from the support 555 by means of a plurality of superimposed layers of insulation designated as 111, 112 and 113, respectively. The insulating layer 113 is directly in engagement with the support 85. A suitable conductor 114 is interposed between the insulating layers 112 and 113, and another conductor 122 is interposed between the insulating layers 111 and 112. These conductors 114 and 122 are suitably insulated from the passageway 183 by an insulating sleeve 116.

it will be apparent that the bimetallic element can be employed to control either one or both the heating element and the motor 53. Preferably the motor 53 is energized whenever the power cord 14 is connected to a suitable power outlet such as 16; or, in other words, the motor 53 is continuously operative when the blanket is in use, and the heating element 99 is controlled in accordance with the desired temperature conditions. As schematically indicated in Fig. 5 of the drawings, the power cord 14 is connected directly to the winding 73 of the motor 53 through a suitable switch 117, which switch may or may not be provided, as the case may be. Connected across the motor windings is a suitable indicating light 118 serially connected with a current limiting resistor 119. Such an indicating means may or may not be provided, but it is desirable to show the operator that the unit is in operation. Such an indicating light can be disposed at any suitable place in the housing 513 and may be associated with an illuminated dial adjacent the knob 13.

In order selectively to control the operation of the heating element 9 a suitable switch comprising relatively movable contacts 120 and 121 is provided. The contact 121 is illustrated as a stationary contact and is suitably supported and electrically connected to the conductor 114-. The contact 121), on the other hand, is illustrated as a movable contact and is supported on a resilient contact arm which is an extension of conductor 122 interposed between insulating layers 112 and 113. The terminal 96 of the heating element 90 is connected by means of the conductor 98 directly to the conductor 114, and hence directly to the stationary contact 121. The terminal 97 of the heating element 9b, on the other hand, is connected by the conductor 99 directly to one line of the power source provided by supply conductor 14. The conductor 122, on the other hand, is connected by means of the conductor 124 with the other side of the power source embodied in power cord 14.

So that the bimetallic element 116 may control the relatively movable contacts 121 and 121, the end of the bimetallic element not rigidly connected to return fluid box 1fr2 is provided with an insulating end portion arseAae;

, 13 125, and the resilient contact arm 122 is provided with a hook-shaped portion 122a. As the temperature of the return fluid from blanket increases, the bimetallic element Mil deflects in an upward direction, as viewed in Fig. 6 of the drawings, with the result that separation of the relatively movable contacts 120 and 121 takes place to deenergize the heating element 90. As soon as the temperature of the returning fluid from the blanket 10 decreases sufficiently, the switch comprising contacts 12% and 12.1 closes to energize the heating element 9t), thereby giving very accurate and improved temperature control with the blanket itself constituting a temperature sensing element and transferring this information to the bimetallic element lit? with high speed and great accuracy.

in order to permit selective control of the temperature of the blanket it), the temperature at which the bimetallic element lid opens the switch comprising contacts 126 and T21 should be adjustable. To this end there is provided a suitable bracket 127 mounted on the support 85. Threadedly mounted in the bracket 12'7 is an adjustable rod rotatably connected to the control knob 13. A lower end of the adjustable rod 128 designated as 128a is engageable with an intermediate portion of the resilient contact arm 122 so that an external force may be applied thereto and, hence, vary the temperature at which the bimetallic element lld is capable of opening the switch comprising contacts 12d and 121. Obviously, any other suitable means for selectively adjusting this temperature may be employed, and the illustrated embodiment is by way of example only.

It will be appreciated that suitable means for fastening the cover 5012 to the container Stia to define the housing will be provided.

With the arrangement described above, it will be apparent that a very efficient sound and vibrationproof control unit 12 is provided. The electrical energy input to the motor 53 that is not used for driving the pump 54 is, obviously, converted to heat, which heat is not lost but is transferred to the circulating fluid 62, which is also used to cool the motor, and, in turn, is then transferred to the blanket 10. It will be apparent that the bimetallic element lit) and the switch comprising contacts 120 and 121 could be contained in a separate control unit, as is the case in connection with presently controlled electric blankets. However, it has been found by experience that once the desired temperature adjustment is made the user seldom thereafter makes any further adjustment. Accordingly, it is believed that the preferable arrangement is that described with everything embodied in the control unit 12.

In view of the detailed description included above, the operation of the thermal blanket of the present invention will readily be understood by those skilled in the art. When the blanket is not in use, it will be emptied of fluid, and the couplings 42 and 43 connected as shown in Fig. 2 of the drawings. In emptying the blanket of fluid, the control unit 12 is merely inverted so that the pump inlet 60 is no longer immersed within the fluid and all the fluid contained in the blanket will be pulled back into the container 52, so that for storage purposes the blanket ltd will have its fluid connections in the condition shown in Fig. 2 of the drawings, and the control unit 12 will have its couplings 10d and 65 also connected together. In use, the power cord 14 is connected to a suitable electric outlet and the switch 117 is closed, whereupon the electric motor 53 will be continuously operative to drive the pump 54. Obviously, the pump could be controlled by the thermostatic control means, just as is the heating element 9%, but the preferable arrangement is believed to be that disclosed. The operator then selectively adjusts the setting of the control knob 13 and the temperature of the return fluid will then control the uniform and accurate heating under all conditions, which will not be affected by drafts or the like as is the case with conventional blankets employed heretofore.

From the above description it will be appreciated that the thermal blanket of the present invention is extremely safe, since there are no electric wires in the blanket which might break and cause arcing and ignition of the blanket. There is, furthermore, no possibility of shock hazard whatsoever. in electric blankets as now constructed, the insu lation absorbs moisture under high humidity conditions, which often exist in connection with bedding due to perspiration of the user, and a considerable amount of leakage current has, therefore, been experienced with such electric blankets. With the present arrangement, there is no possibility of such leakage currents, and there is no possibility that hot spots in the blanket can be obtained if the blanket is folded double or if the user should happen to fold it under himself, as could occur with the conventional type of electric blanket. Even though the conventional electric blankets have a large number of so-called safety thermostats, there is no assurance that these thermostats will respond to hot spots which happen to occur between the thermostats. This is because the blanket material is such a poor heat conductor that a hot spot or even actual combustion a few inches away from a thermostat would not even affect the thermostat.

Another feature of the present invention resides in the provision of a thermal blanket which is very light in weight. One of the talking points of electric blankets sold heretofore is the fact that only one very light blanket need be employed. However, the copper conductors employed in such blankets actually are heavier than the weight of the passageways and circulating fluid in the blanket of the present invention. Thus, even a lighter weight blanket is provided.

The blanket of the present invention provides the ultimate in comfort with much more even heat than was possible by means of a conventional electric blanket. First of all, there is no possibility of hot spots due to folding or the like, as mentioned above, and by virtue of the fluid in the blanket if; being a very excellent temperature sensing device a much more even heat and more accurate control is obtained unaffected by drafts or other conditions.

A very efficient and quiet pump unit is provided, which continually circulates without noise or vibration at fluid through the blanket, which fluid could be a cooling fluid as well as a heating fluid, thus having a substantial advantage over an electric blanket which can only be a heating blanket. The person using the thermal blanket of the present invention, whether for heating or for cooling purposes, will feel completely at ease by using such blanket, since there is no possibility of starting an electrical fire or obtaining an electrical shock. It will, moreover, be apparent from the above description that a substantially uniform temperature throughout the entire area of the blanket is obtained.

While there has been illustrated and described what is at present considered to be the preferred embodiment of the present invention, it will readily be understood that numerous changes and modifications will occur to those skilled in the art, and it is aimed in the appended claims to cover all such changes and modifications as will within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. A thermal blanket comprising two fabric members united by a plurality of spaced parallel stitchings thereby to define a plurality of parallel passageways between said fabric members, a pair of flexible headers extending along one end of said blanket and generally perpendicular to said passageways, a plurality of flexible tubes of U shape, having the legs of the U disposed in said passageways and one leg of each U being connected to one of said headers, while the other leg of each U is connected to the other header, whereby all of said tubes are connected in parallel, and means for circulating a fluid medium through said headers and tubes.

2. A thermal blanket comprising a fabric having a plurality of parallel passageways defined therein, a pair of flexible headers extending along one end of said blanket and generally perpendicular to said passageways, a plurality of flexible tubes of U shape, having the legs of each U disposed in passageways and one leg of each U being connected to one of said headers, while the other leg of each U is connected to the other header, whereby all of said tubes are connected in parallel, means for circulating a fluid medium through said headers and tubes, and control means for controlling the temperature of said blanket. I

3. A thermal blanket comprising two fabric members united by a plurality of spaced parallel stitchings thereby to define a plurality of parallel passageways between said fabric members, a pair of flexible headers extending along one end of said blanket and generally perpendicular to said passageways, a plurality of flexible tubes of U shape, having the legs of the U disposed in said passageways and one leg of each U being connected to one of said headers, while the other leg of each U is connected to the other header, whereby all of said tubes are connected. in parallel, means connected to said headers at a point midway between the ends thereof for circulating a fluid medium through said headers and tubes, and control means for controlling the temperature of said blanket.

4. A thermal blanket comprising a fabric member having a plurality of parallel passageways defined therein, a pair of flexible headers extending along one end of said blanket and generally perpendicular to said passageways, a plurality of flexible tubes of U shape, having the legs of the U disposed in said passageways and one leg of each U being connected to one of said headers, while the other leg of each U is connected to the other header, whereby all of said tubes are connected in parallel, means for circulating a fluid medium through said headers and tubes, and control means responsive to the temperature of the fluid in one of said headers for controlling the temperature of said blanket.

5. A thermal blanket comprising two fabric members united by a plurality of spaced parallel stitchings thereby to define a plurality of parallel passageways between said fabric members, a pair of flexible headers extending along one end of said blanket and generally perpendicular to said passageways, a plurality of flexible tubes of U shape, having the legs of the U disposed in said passageways and one leg of each U being connected to one of said headers, while the other leg of each U is connected to the other header, whereby all of said tubes are connected in parallel, means for circulating a fluid medium through said headers and tubes, and control means for controlling the temperature of said blanket in response to the temperature of the fluid in one of said headers.

6. A blanket comprising a fabric member having a plurality of parallel connected tubular fluid passageways defined therein, said tubular passageways comprising plastic tubing having an internal diameter of between 0.025 and 0.075 of an inch and a wall thickness of between 0.016 and 0.030 of an inch.

7. A blanket comprising a fabric member having a plurality of parallel connected tubular passageways defined therein, said tubular passageways comprising polyvinyl chloride tubing having an internal diameter of between 0025 and 0.075 of an inch and a wall thickness of between 0.016 and 0.030 of an inch.

8. A blanket comprising a. fabric member having a plurality of parallel connected U-shaped tubular passageways defined therein, said tubular passageways comprising plastic tubing having an internal diameter of between 0.025 and 0.075 of an inch and a wall thickness of between 0.016 and 0.030 of an inch, 21 pair of headers each connected to all of said U-shaped tubular passageways, said headers comprising plastic tubing having an internal 16 diameter of between 0.09 and 0.2 of an inch and a wall thickness of between 0.02 and 0.05 of an inch.

9. A blanket including a fabric, a plurality of tubular passageways enclosed in said fabric, said tubular passageways comprising a pair of headers and a plurality of U shaped tubes connected between said headers and in paral lel with each other, the legs of said U-shaped tubes being disposed in spaced parallel relationship, whereby even though a substantial temperature differential exists between the fluid entering and leaving said tubes the average temperature produced by the adjacent legs of said tubes is equal throughout the extent thereof, whereby said blanket is maintained at a uniform temperature throughout.

10. A blanket including a fabric, a plurality of tubular passageways enclosed in said fabric, said tubular passageways comprising a pair of headers and a plurality of U- shaped tubes connected between said headers and in paral-.

lel with each other, and means for circulating a heat transfer medium through said passageways, the legs of said U-shaped tubes being disposed in spaced parallel relationship, whereby even though a substantial differential exists between the fluid entering and leaving said tubes the average temperature produced by the adjacent legs of each tube is equal throughout the extent thereof, whereby said blanket is maintained at a uniform temperature throughout.

ll. A thermal blanket comprising a fabric element having a plurality of flexible fluid-carrying passages defined therein through which a heat transfer fluid can flow, a control unit including a housing having an electric motor and a pump driven thereby disposed therein, said housing being located remotely relative to said blanket, flexible conduits for connecting said control unit and said blanket to transfer fluid between said control unit and said blanket, means in said control unit for preventing noise and vibrations produced therein from being transmitted to outside said housing, and means for utilizing said circulating fluid to cool said electric motor.

12. A thermal blanket comprising a fabric bed cover having a plurality of flexible fluid-carrying passages defined therein through which a heat transfer fluid can flow, a control unit including an electric motor and a pump driven thereby located remotely relative to said blanket, flexible conduits for connecting said control unit and said blanket, a hydrocarbon liquid heat transfer fluid in said passages and control unit, means in said control unit for preventing noise and vibrations produced therein from being transmitted to the surrounding air, and means for utilizing said circulating fluid to cool said electric motor.

13. In combination, a blanket comprising a fabric element having a plurality of flexible fluid-carrying passageways defined therein through which a heat transfer fluid can flow, a control unit including an outer housing and an inner sealed casing within said housing, fluid circulating means disposed within said casing, flexible conduits for connecting said fluid circulating means and said blanket to transfer fluid between said control unit and said blanket, and spring means for supporting said casing within said housing to prevent vibrations produced by said fluid circulating means from being transmitted to said housing.

14. The combination of claim 13 wherein said spring means are tension springs suspending said casing within said housing.

15. The combination of claim 13 wherein said spring means are tension springs suspending said casing within said housing, and stop means are provided to limit the relative movement between said casing and housing when said control unit is inverted.

l6. In combination, a bed cover having a plurality of flexible fluid-carrying passageways defined therein through which a heat transfer fiuid can flow, a control unit including a housing having an electric motor and a pump driven thereby disposed therein, conduit means for connecting said control unit and said passageways to transfer fluid between said control unit and said passageways, said passageways, conduit means and pump defining a fluid circuit, a heat transfer liquid in said fluid circuit, and means for causing said circulating liquid to contact said motor to cool the same.

17. The combination of claim 16 wherein heating means are included in said control unit for heating said liquid.

18. The combination of claim 16 wherein temperature changing means are included in said control unit to change the temperature of said liquid, and said temperature changing means is controlled in response to the tempera ture of the liquid returned from said passageways to said control unit.

19. In a thermal blanket comprising a fabric member having a plurality of flexible fluid-carrying passageways defined therein through which a heat transfer fluid can flow, a housing, a fluid circulating pump in said housing, an electric motor in said housing drivingly connected to said pump, a sealed casing mounted within said housing enclosing said pump and motor, conduit means for connecting said casing and said passageways to transfer fluid between said control unit and said fabric member, said fluid passageways, conduit means and sealed casing defining a fluid circuit, a heat transfer liquid in said fluid circuit capable of all being contained in said casing, electric heating means for heating said liquid in said casing, an energization circuit for said electric motor and said electric heating means including an electric switch in series with said electric heating means, means defining a fluid chamber in said housing through which liquid returning from said passageways to said casing must flow, the outlet to said fluid chamber being smaller than said inlet whereby said fluid chamber is maintained full of liquid returning from said passageways when said motor is energized, and temperature responsive means responsive to the temperature of the liquid in said chamber for controlling said switch.

20. A thermal blanket comprising a fabric member having a plurality of flexible fluid-carrying passageways defined therein through which a heat transfer fluid can flow, a housing, a fluid circulating pump in said housing, an electric motor in said housing drivingly connected to said pump, a sealed casing mounted within said housing enclosing said pump and motor, conduit means for connecting said casing and said passageways to transfer fluid between said control unit and said fabric member, said fluid passageways, conduit means and sealed casing defining a fluid circuit, a heat transfer liquid in said fluid circuit capable of all being contained in said casing, said pump having an inlet immersed in said liquid, electric heating means for heating said liquid in said casing, an energization circuit for said electric motor and said electric heating means including an electric switch in series with said electric heating means, said electric motor being continuously operative when electric power is supplied to said energization circuit, and temperature responsive means responsive to the temperature of the liquid returned to said casing from said passageways for controlling said switch and hence the temperatue at which said fabric member is maintained.

21. The thermal blanket of claim 19 wherein the outlet to said fluid chamber is disposed over said electric motor whereby said returning liquid cools the windings of said motor.

22. The thermal blanket of claim 20 wherein the liquid returned to said casing cools said electric motor.

23. A bed cover comprising a flexible layer of fabric, means defining a plurality of flexible fluid-carrying passageways Within said fabric, pump means, flexible conduit means defining a supply conduit and a return conduit interconnecting said pump means and said passageways, and coupling means in each of said supply conduit and said return conduit whereby said pump means may be connected and disconnected from said bed cover, said coupling means being so constructed and arranged to permit interconnection of the coupling ends of said supply and return conduits when said pump means is disconnected from said blanket to maintain a closed fluid circuit for the passageways of said cover as Well as said pump means.

24. In combination, a bed cover having a plurality of flexible fluid-carrying passageways defined therein through which a heat transfer fluid can flow, a control unit including a housing having an electric motor and a pump driven thereby disposed therein, conduit means for connecting said control unit and said blanket to transfer fluid between said control unit and said bed cover, said passageways, conduit means and pump defining a fluid circuit, a heat transfer liquid in said fluid circuit, and heating means for heating said liquid, the electric energy input to said motor not used to drive said pump being converted to heat energy to heat said liquid thereby supplementing the heating of said liquid by said heating means.

25. The blanket of claim 9 wherein said tubular passageways are formed of polyvinyl chloride type of plastic.

26. In a thermal blanket comprising a fabric member having a plurality of flexible fluid-carrying passageways defined therein through which a heat transfer fluid can how, a housing, a fluid circulating pump in said housing, an electric motor in said housing drivingly connected to said pump, a sealed casing mounted within said housing enclosing said pump and motor, conduit means for connecting said casing and said passageways to transfer fluid between said control unit and said fabric member, said n'tud passageways, conduit means and sealed casing defining a fluid circuit, a heat transfer fluid in said fluid circult, temperature changing means for changing the temperature of said liquid in said casing, an energization circuit for said electric motor and said temperature changing means including an electric switch in series Wllil the electrical circuit of said temperature changing means, temperature responsive means responsive solely to the temperature of the liquid returning to said casing for controlling said switch, and means for selectively controlling said temperature responsive means.

27. in a thermal blanket comprising a fabric member having a plurality of flexible fluid-carrying passageways defined therein through which a heat transfer fluid can ilow, a housing, a fluid circulating pump in said housing, an electric motor in said housing drivingly connected to said pump, a sealed casing mounted within said housing enclosing said pump and motor, conduit means for connecting said casing and said passageways to transfer fluid between said control unit and said fabric member, said fluid passageways, conduit means and sealed casing delining a fluid circuit, a heat transfer fluid in said fluid circuit, electric heating means for heating said liquid in said casing, an energization circuit for said electric motor and said electric heating means including an electric switch in series with said electric heating means, temperature responsive means within said housing responsive solely to the temperature oi the liquid returning to said casing for controlling said switch, and manually adjustable means on said housing for selectively controlling said temperature responsive means.

28. A bed cover comprising a flexible layer of fabric, means defining a plurality of flexible fluid carrying passageways within said fabric, a totally enclosed pump unit remotely disposed relative to said bed cover, flexible conduit means interconnecting said pump unit and said passageways, a heat transfer liquid circulated through said passageways by said pump unit, means for varying the temperature of said heat transfer liquid, and means responsive directly to the temperature of the liquid returning from said flexible fluid carrying passageways for controlling said means for varying the temperature.

29. The blanket of claim 8 wherein the connection between said plastic U-shaped tubular passageways and said plastic headers is a heat sealed connection.

30. A bed cover comprising a flexible layer of fabric, means defining a plurality of flexible fluid carrying passageways associated with said fabric, fluid circulating means remotely disposed relative to said bed cover for circulating a heat transfer liquid through said passageways, flexible conduit means interconnecting said fluid circulating means and said passageways associated with said fabric, temperature responsive means responsive directly to the temperature of the heat transfer liquid returning from said flexible fluid carrying passageways, temperature varying means for varying the temperature of said heat transfer liquid, and means responsive to said temperature responsive means for controlling said temperature varying means.

31. A. bed cover comprising a flexible layer of fabric, means defining a plurality of flexible fluid carrying passageways associated with said fabric, a fluid circulating element remotely disposed relative to said bed cover for circulating a heat transfer liquid through said passageways, flexible conduit means interconnecting said fluid circulating element and said passageways associatedture of said heat transfer liquid, and means responsive to said temperature responsive means for controlling one. of said elements.

References Cited in the file of this patent UNITED STATES PATENTS 1,896,853 Hassell Feb. 7, 1933 1,970,200 Short Aug. 14, 1934 2,250,325 Barnes July 22, 1941 2,259,712 Sweetland Oct. 21, 1941 2,617,915 Blair Nov. 11, 1952. 2,690,327 Sardeson Sept. 28, 1954 FOREIGN PATENTS 215,358 Switzerland Jan. 16, 1942 

